Dental restoration is an important and highly technical subcategory of the dental specialty of prosthodontics. Many important and significant developments have occurred in this field since the days of President Washington and his set of wooden dentures. Although conventional cemented or removable prosthetic devices, for example, bridges, partial dentures, and complete dentures, are still used widely in dentistry, it is now more and more prevalent to find dental patients receiving permanently implanted individual replacement teeth. In many cases such permanent replacement teeth are preferred over removable prostheses, but at the present time the process involved in the actual fitting of permanently implanted replacement teeth is quite complicated and difficult to perform with accurate results.
The fitting of an implant-retained replacement tooth in place of a missing tooth in a patient's mouth requires several complicated steps. In order to anchor the replacement tooth in the patient's mouth, an implant must be placed into the patient's jaw. This implant will provide an anchoring device for the abutment(s) and screw(s) which will eventually hold the replacement tooth. However, it is difficult to properly locate sufficient maxillary or mandibular bone in which to fix the implant so that optimum security and positioning of the replacement tooth is achieved. Due to the fact that the bone structure and the density or mass of the underlying bone is not readily apparent on radiographs, implants are frequently positioned in a location where the bone structure is insufficient to form a proper anchoring position for the implant. This can ultimately lead to the failure of the implant. In addition, if the implant is seated at an improper angle an unaesthetic cosmetic appearance is achieved and, perhaps more importantly, improper occlusion results.
U.S. Pat. No. 5,015, 183, issued to Fenick, partially addressed some of the earlier problems in the placing of such implants. That patent describes a method and device for placing an implant or artificial tooth in optimal bone structure by providing a radiology stent with a radiopaque grid contained within the stent. The stent is placed in the vicinity of the void where the implant is to be placed. A series of x-rays at oblique angles at spaced intervals along the implant provides grid points for determining the optimum trajectory of the proposed implant. The angles are then related to a formed surgical stent having a guide for directing a drill bit in the direction established by the radiology stent. In this device, and in other devices typically used in determining angle of placement of abutments for implants, metal wires serve as the radiopaque materials. Alternatively, in some cases, metal spheres may also serve as radiopaque markers. A principal disadvantage of the use of metal in x-ray radiography is that the metal can introduce distortional artifacts on the final radiograph. When angle of drilling trajectory is calculated based upon x-ray radiographs, such distortion can introduce significant error. As noted above, such error can lead to placement of abutments in bone of less than optimal mass or density, and/or at improper angles.
In addition, positioning of radiopaque metal wires or spheres in a stent such as that described in U.S. Pat. No. 5,015,183 does not provide an optimally accurate positioning vis-a-vis the gingival surface and the base of the replacement tooth. This can introduce further drilling error, further seating error, and once again can lead to a less than optimal anchoring of the replacement tooth. Furthermore, use of such a stent cannot provide an optimally accurate indication of the ultimate anatomical configuration of the replacement tooth. Without a knowledge of this final configuration, the best drilling angle may still not be achieved, and the best occlusal positioning may not be possible. This is due to the fact that peculiarities of tooth shape, occlusal angles, etc., in the final replacement implant may be such that an oral surgeon cannot use the most advantageous drilling angles for that particular tooth, even if those angles have been correctly calculated. Using a stent such as those known in the prior art in determining those drilling angles does not allow an oral surgeon to appropriately compensate for anatomical peculiarities.
Additionally, the method of making tooth-shaped forms currently recognized in the art is a complicated process involving several steps. First, the patient's dentist would make an impression of the patient's teeth. That impression would then be provided to a laboratory technician who would make stone models based upon the impression. The replacement teeth would then be designed and fabricated in wax from the stone mold. This multi-step process introduces error and variance in the size, shape, and most importantly in the occlusal conformation of the replacement tooth. It is also a time-consuming operation and an especially inefficient means of making forms for individual teeth.
Therefore, a significant need exists for a reference device for radiography that will provide a more accurate determination of proper drilling angles for better positioning of implants, and which does not create the distortion of x-ray images which can be generated by metallic objects. Ideally, such a reference device would be tooth shaped and would be made of a material which could be easily sculpted or modified in shape after it is molded so that it can serve not only as a radiopaque reference device for determination of drilling angles on a radiograph, but also as an accurate indicator of the final anatomical form and shape of the replacement tooth. The latter advantage would allow an oral surgeon to interpret simultaneously not only the proper angles for drilling vis-a-vis the underlying bone structure but also to take into account any peculiarities in the tooth shape which might require adjustment of those angles for the final drilling process.